grammar - Whether you need the word 'to' in the sentence - Which place do you want to go to?

Which sentence is correct and why?

1. Which do you want to go to?


2. Which do you want to go?

I am a native English speaker and was asked this by a Japanese person. I think number 2 is not correct but I don't know the reason why, or if in fact I am actually right.

Thanks!